1. Field of the Invention
This invention relates to a photographic processing method for silver halide color photographic materials, and more particularly to a photographic processing method for silver halide color photographic materials having a sufficient bleaching activity and capable of forming color images having good image quality. More specifically, the invention relates to a method for stably maintaining the function of bleach solution by replenishing a bleach solution which has a sufficient bleaching activity but is unstable during prolonged photographic processing.
2. Description of the Prior Art
In photographic processing of silver halide color photographic materials, after imagewise exposure, the silver halide color photographic material (the silver halide emulsions of which may have been previously fogged) is usually developed in a developer (i.e., a developing solution) containing an aromatic primary amine color developing agent in the presence of dye-forming couplers to form a color image, and thereafter developed silver formed simultaneously is rehalogenated by bleaching and removed together with undeveloped silver halide by fixing (combined bleaching and fixing steps are referred to as "blixing").
An organic acid such as an aminopolycarboxylic acid-metal complex used as a bleaching agent for a bleach solution causes less environmental pollution, especially water pollution, than earlier methods, and hence such an organic acid-metal complex has frequently been used as a bleaching agent. However, an organic metal complex generally has a relatively low oxidizing power and may have insufficient bleaching power. Hence, although when a bleach solution containing such a bleaching agent is used for bleaching low speed silver halide color photographic materials having mainly, for example, silver chlorobromide emulsion layers, the desired object may be satisfactorily attained, when the bleach solution is used for processing high speed silver halide color photographic materials having mainly dye-sensitized silver iodochloride or silver iodobromide emulsion layers, and, in particular, high speed silver halide color photographic materials having high silver content silver halide emulsion layers (by expression "high silver content silver halide emulsion layers" is meant silver halide emulsion layers wherein the total amount of silver in the blue-sensitive, green-sensitive, and red-sensitive silver halide emulsion layers is more than about 20 mg per 100 cm.sup.2), the bleaching action by the bleaching agent is insufficient, causing poor silver removal and so-called poor recoloring (that is, a state wherein dyes formed by the oxidation coupling of the oxidation product of a color developing agent and couplers remain in the state of leuco dyes, which are reaction intermeidates, after bleaching, and thereby complete dyes are not formed). These difficulties must be overcome to attain the rapid processing of high speed silver halide color photographic materials.
As a method of overcoming these difficulties, it has been proposed in Japanese Patent Application (OPI) No. 109731/75 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") to add hydrogen peroxide to an organic acid iron or cobalt complex salt. Such bleach solution is generally subject to the fatal defect that leuco dyes may be converted into dyes when silver halide color photographic materials are processed by the bleach solution immediately after the preparation thereof, but when the bleach solution is allowed to stand after the preparation thereof, the oxidizing power of the bleach solution decreases rapidly with the passage of time. Thus the oxidation of silver and leuco dyes becomes insufficient, and this defect occurs even under acidic conditions (pH 2 to 6) in which the bleach solution is relatively stable. This defect is believed to be caused by the decomposition of hydrogen peroxide in the bleach solution, promoted by metal ions.
Also, the use of a large amount of an aminopolycarboxylic acid iron complex is undesirable not only from an environmental viewpoint, since in such a case the concentration of iron ions increases, but also from an economic viewpoint, in that the costs for raw materials increase.
On the other hand, since hydrogen peroxide decomposes to form water, it is an ideal oxidizing agent which causes no environmental pollution. Therefore, it has long been desired in the field of the art to achieve practical use of a bleach solution using hydrogen peroxide for color photography.
However, although hydrogen peroxide is a strong oxidizing agent, it is practically impossible to bleach silver in color photographic materials using hydrogen peroxide alone as a bleaching agent.
As a method of solving the foregoing difficulties, it has been proposed to add a relatively small amount of an inorganic metal salt to a bleach solution containing hydrogen peroxide, as disclosed in Japanese Patent Application (OPI) No. 1026/79. However, in the above-described method the hydrogen peroxide in the bleach solution is liable to decompose, making it difficult to maintain the function of the bleach solution at a constant level for a longer period of time than one month, and hence the method is difficult to use from a practical viewpoint.
For use of an etching bleach solution, it is proposed to use hydrogen peroxide in combination with a stabilizer composition comprising citric acid and polyalkylene oxide as stabilizers (Japanese Patent Application (OPI) No. 149401/78).
Hitherto, it has been practiced, to keep the function of not only a bleach solution, but also other photographic processing solution baths, at constant level by adding a replenishing solution having the same as or a similar composition to that of the bleach solution or other processing solution to the processing bath. However, since the bleach solution using hydrogen peroxide and a metal salt is very poor in stability, it is not practically possible to maintain the function of a bleach solution at a constant level even by performing the replenishing of the processing composition in a conventional manner.